Transmitting system, transmission slotting apparatus, receiving apparatus, and transmission slot generating method

ABSTRACT

A transmitting system includes a variable-length packet multiplexing apparatus and a transmission slotting apparatus. The variable-length packet multiplexing apparatus generates a variable-length packet. The transmission slotting apparatus stores the variable-length packet in slots forming transmission main signals. The transmission slotting apparatus includes a capacity calculator, an extractor, a remainder calculator, a selector, and a slot information multiplexer. The capacity calculator calculates a data capacity of the transmission main signals for one frame. The extractor extracts a byte number of the variable-length packet. The remainder calculator calculates a remaining capacity of the transmission main signals. The selector stores a predetermined data sequence in a region left in the slots, and outputs the slots storing the data sequence. The slot information multiplexer multiplexes slot information and the slots output by the selector.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of U.S. Ser. No. 15/706,068filed Sep. 15, 2017, which is a Continuation Application of PCTApplication No. PCT/JP2015/085702, filed Dec. 21, 2015 and based uponand claiming the benefit of priority from prior Japanese PatentApplication No. 2015-053838, filed Mar. 17, 2015, the entire contents ofeach of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a transmitting system,a transmission slotting apparatus, a receiving apparatus, and atransmission slot generating method.

BACKGROUND

In broadcasting systems at present, Moving Picture Experts Group-2Transport Stream (MPEG-2 TS) and Real-time Transport Stream (RTP) mediatransport schemes are being widely used. These schemes, however, facevarious limitations if cooperation between broadcasting andcommunication is attempted. So, MPEG Media Transport (MMT) has beenproposed as a new media transport scheme that assumes the use of variousnetworks with MPEG.

An MMT-adopted transmitting system converts MPEG Media TransportProtocol (MMTP)/User Datagram Protocol (UDP)/Internet Protocol (IP)packets into Type Length Value (TLV) packets. The transmitting systemstores TLV packets in slots to generate transmission main signals. Thetransmission main signals are generated in units of slots, and theirtransmission control setting is updated for each frame of 120 slots, forexample. The transmitting system performs modulation processes, etc. onthe transmission main signals and transmits them as broadcast waves.

When a transmitting system generates transmission main signals bystoring TLV packets in slots, the transmission main signals for a framemay have a last valid slot with a remaining capacity of less than 4bytes. Unfortunately, a TLV packet requires a minimum capacity of 4bytes, and if the slot's remaining capacity falls below 4 bytes, it isno longer possible to store a TLV packet in that slot. Such an instancemay pose problems for the transmitting system to transmit broadcastwaves.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a transmitting system and areceiving system according to a first embodiment.

FIG. 2 is a diagram illustrating a structure of a TLV packet generatedby the TLV multiplexing apparatus of FIG. 1.

FIG. 3 is a diagram illustrating a structure of a slot according to thefirst embodiment.

FIG. 4 is a block diagram illustrating an exemplary functionalconfiguration of the transmission slotting apparatus of FIG. 1.

FIG. 5 is a diagram illustrating slot structures of the transmissionmain signals output from the slot information multiplexer of FIG. 4 tothe transmission processing apparatus.

FIG. 6 is a flowchart showing the processes to perform when the selectorof FIG. 4 stores received data in slots.

FIG. 7 is a diagram illustrating the transmission main signals outputfrom the selector of FIG. 4.

FIG. 8 is a diagram illustrating another example of the transmissionmain signals output from the selector of FIG. 4.

FIG. 9 is a diagram illustrating yet another example of the transmissionmain signals output from the selector of FIG. 4.

FIG. 10 is a block diagram illustrating a configuration of the receivingsystem of FIG. 1.

FIG. 11 is a block diagram illustrating a functional configuration ofthe transmission main signal receiving apparatus of FIG. 10.

FIG. 12 is a block diagram illustrating an exemplary functionalconfiguration of a transmission slotting apparatus according to a secondembodiment.

FIG. 13 is a flowchart showing the processes to perform when theselector of FIG. 12 stores received data in slots.

DETAILED DESCRIPTION

In general, according to one embodiment, a transmitting system includesa variable-length packet multiplexing apparatus and a transmissionslotting apparatus. The variable-length packet multiplexing apparatusgenerates a variable-length packet comprising information indicative ofa type of data and information indicative of a byte number of the data.The transmission slotting apparatus stores the variable-length packet inany of a plurality of slots forming transmission main signals. Thetransmission slotting apparatus includes a capacity calculator, anextractor, a remainder calculator, a selector, and a slot informationmultiplexer. The capacity calculator receives setting information forthe transmission main signals for one frame, and calculates, based onthe setting information, a data capacity of the transmission mainsignals for one frame. The extractor extracts a byte number of thevariable-length packet. The remainder calculator calculates a remainingcapacity of the transmission main signals based on the data capacitycalculated by the capacity calculator and the byte number extracted bythe extractor. The selector stores a predetermined data sequence in aregion left in the slots if the remaining capacity of the transmissionmain signals having stored the variable-length packet in any of theslots is less than a minimum byte number of a variable-length packet,and outputs the slots storing the data sequence. The slot informationmultiplexer multiplexes slot information and the slots output by theselector.

Hereinafter, embodiments will be described with reference to theaccompanying drawings.

First Embodiment

FIG. 1 is a block diagram illustrating a transmitting system 10 and areceiving system 20 according to the first embodiment. The transmittingsystem 10 transmits broadcast waves. The transmitted broadcast wavesreach the receiving system 20 via transmission channels such as abroadcast network. The receiving system 20 receives the broadcast waves.

[Transmitting System 10]

The transmitting system 10 shown in FIG. 1 includes an encoder 11, anadditional information generating apparatus 12, an MPEG Media Transport(MMT) multiplexing apparatus 13, an Internet Protocol (IP) multiplexingapparatus 14, a Type Length Value (TLV) multiplexing apparatus 15, atransmission slotting apparatus 16, and a transmission processingapparatus 17.

The encoder 11 receives video and/or audio signals from, for example,imaging apparatuses such as a camera, or a server, etc. The encoder 11encodes the received video and/or audio signals based on preset methodsto convert them into encoded signals. The encoder 11 outputs the encodedsignals to the MMT multiplexing apparatus 13.

The additional information generating apparatus 12 generates informationincluding broadcast program guides, information on accounting,encryption, etc. of distribution video content, and so on, and outputsthem as additional information to the MMT multiplexing apparatus 13.Although FIG. 1 does not show an encryptor (scrambler) in thetransmitting system 10, an encryptor may be provided, for example,between the MMT multiplexing apparatus 13 and the IP multiplexingapparatus 14.

The MMT multiplexing apparatus 13 includes, for example, a CentralProcessing Unit (CPU), a memory for use with the CPU's processing, and aField Programmable Gate Array (FPGA), etc. to perform given processingunder the control of the CPU. With the CPU causing the FPGA to performthe given processing, the MMT multiplexing apparatus 13 processes theencoded signals. Specifically, the MMT multiplexing apparatus 13 addsthe additional information to the encoded signals, and stores theadditional information-added encoded signals in an MPEG Media TransportProtocol (MMTP) packet. The MMT multiplexing apparatus 13 outputs theMMTP packet to the IP multiplexing apparatus 14.

Note that the MMT multiplexing apparatus 13 may include a Large-ScaleIntegration (LSI) instead of the FPGA. Also, the MMT multiplexingapparatus 13 may perform the given processing by software.

The IP multiplexing apparatus 14 includes, for example, a CPU, a memoryfor use in the CPU's processing, and an FPGA, etc. to perform givenprocessing under the control of the CPU. With the CPU causing the FPGAto perform the given processing, the IP multiplexing apparatus 14processes the MMTP packet. Specifically, the IP multiplexing apparatus14 stores the MMTP packet in an IP packet. The IP multiplexing apparatus14 outputs the IP packet to the TLV multiplexing apparatus 15.

The IP multiplexing apparatus 14 may include an LSI instead of the FPGA.Also, the IP multiplexing apparatus 14 may perform the given processingby software.

The TLV multiplexing apparatus 15 includes, for example, a CPU, a memoryfor use in the CPU's processing, and an FPGA, etc. to perform givenprocessing under the control of the CPU. With the CPU causing the FPGAto perform the given processing, the TLV multiplexing apparatus 15processes the IP packet. Specifically, the TLV multiplexing apparatus 15generates a TLV packet based on the IP packet.

FIG. 2 is a schematic diagram illustrating a structure of the TLV packetgenerated by the TLV multiplexing apparatus 15. As shown in FIG. 2, theTLV packet consists of 2 bits for “01”, 6 reserved bits for “111111”, 8bits for “packet type” for identifying the type of the packet stored inTLV, 16 bits for “data length” for writing the byte number of thesucceeding data, and the data that has the byte number indicated by thedata length. If the data length is 0, that is, the data has a bytenumber 0, the TLV packet accounts for the minimum volume of 4 bytes (2bits+6 bits+8 bits+16 bits+0 byte).

The TLV multiplexing apparatus 15 outputs the TLV packet to thetransmission slotting apparatus 16.

The TLV multiplexing apparatus 15 may include an LSI instead of theFPGA. Also, the TLV multiplexing apparatus 15 may perform the givenprocessing by software.

The transmission slotting apparatus 16 includes, for example, a CPU, amemory for use in the CPU's processing, and an FPGA, etc. to performgiven processing under the control of the CPU. With the CPU causing theFPGA to perform the given processing, the transmission slottingapparatus 16 processes the TLV packet. Specifically, the transmissionslotting apparatus 16 stores the TLV packet in any of the slots thatform transmission main signals, and thereby generates the transmissionmain signals. The transmission slotting apparatus 16 outputs thegenerated transmission main signals to the transmission processingapparatus 17.

The transmission main signals are generated in units of slots.Transmission mode setting for the transmission main signals is updatedfor each frame of 120 slots, based on setting information. The settinginformation includes information about transmission modes, such asmodulation schemes and coding rates, for the 120 slots in thetransmission main signals.

The transmission processing apparatus 17 includes, for example, amodulator and a power amplifier. Signals amplified by the poweramplifier serve as broadcast waves.

FIG. 3 is a schematic diagram showing an exemplary structure of theslots. The slot may be understood as a signal having a slot header and amain signal portion, to which an error correction outer code, stuffbits, and further an error correction inner code are added. The mainsignal portion stores at least one of a TLV packet that contains an MMTPpacket, a TLV packet that contains an NTP (Network Time Protocol)packet, a TLV NULL packet, and slot padding bytes as will be discussed.

FIG. 4 is a block diagram illustrating an exemplary functionalconfiguration of the transmission slotting apparatus 16 shown in FIG. 1.FIG. 4 shows a slot number counter 161, a setting information receiver162, a capacity calculator 163, a transmission slotter 164, a TLV packetreceiver 165, an NTP packet generator 166 where the generated NTP packetis contained in a TLV packet, a slot padding byte generator 167, and aTLV NULL packet generator 168, and each of these functions is realizedby the CPU causing the FPGA to perform given processing. Thetransmission slotting apparatus 16 may include an LSI instead of the CPUand the FPGA in order to realize the functions shown in FIG. 4. Thetransmission slotting apparatus 16 may also realize the functions shownin FIG. 4 by software.

The slot number counter 161, upon receipt of a frame synchronizationsignal, sets a count value to 1 and then restarts counting using atransmission clock. Upon passage of the clock count for the transmissionof data having the slot structure of FIG. 3, the slot number counter 161increments the slot number by 1 and counts the clock for thetransmission of the next slot. This will allow the counting to startconcurrently with the start of the frame. The slot number counter 161outputs the count value to the capacity calculator 163 and a selector1641.

The setting information receiver 162 receives setting information forthe transmission main signals to set the transmission mode for eachframe. The setting information receiver 162 outputs the settinginformation to the capacity calculator 163 and the transmission slotter164.

The coding rate contained in the setting information can be set as, forexample, the coding rates shown in FIG. 3. The bit number of the mainsignals will vary according to the variation in coding rate.

Also, the modulation scheme contained in the setting information may be,for example, 16 amplitude phase shift keying (16APSK), 8 phase shiftkeying (8PSK), quadrature phase shift keying (QPSK), π/2-shift binaryphase shift keying (π/2-shift BPSK), etc. If there are 5 slot unitsunder the 16APSK, 4 slots are valid and 1 slot is invalid. Also, ifthere are 5 slot units under the 8PSK, 3 slots are valid and 2 slots areinvalid. If there are 5 slot units under the QPSK, 2 slots are valid and3 slots are invalid. If there are 5 slot units under the π/2-shift BPSK,1 slot is valid and 4 slots are invalid. The total bit number of themain signals for every 5 slots is determined according to thecombination of the modulation scheme and the coding rate contained inthe setting information.

It is not a limitation that the setting information contains only onecombination of the modulation scheme and the coding rate. The settinginformation may contain two or more combinations of the modulationscheme and the coding rate. If there are more than one combination, thetransmission mode is assigned to slots sequentially in an ascendingorder from the slot number 1, using the combination with a modulationscheme having a larger multi-value first or, if the modulation schemesare the same, using the combination with a higher coding rate first.

The capacity calculator 163 receives the count value from the slotnumber counter 161 and the setting information from the settinginformation receiver 162. The capacity calculator 163, upon receivingthe initial count value for the frame, i.e. “1”, calculates the capacityof the valid main signal portion for the frame as a frame main signalcapacity, based on the bit number of the main signals determined by thecoding rate and the ratio between valid slots and invalid slotsdetermined by the modulation scheme. Also, the capacity calculator 163,upon receiving the count value from the slot number counter 161,calculates the capacity of the valid main signal portion in the slotrepresented by the number of the count value, as a slot main signalcapacity. After calculating the frame main signal capacity and the slotmain signal capacity, the capacity calculator 163 outputs theinformation of these calculated capacities to the transmission slotter164.

If two or more combinations of the modulation scheme and the coding rateare contained in the setting information, the capacity calculator 163calculates a pseudo-frame main signal capacity for each combination. Thecapacity calculator 163 uses a pseudo-slot main signal capacity for theslot start point assigned according to the combination of the modulationscheme and the coding rate contained in the setting information.

The TLV packet receiver 165 receives the TLV packet from the TLVmultiplexing apparatus 15. The TLV packet receiver 165 includes a buffer(not illustrated) and retains the received TLV packet in the buffer. TheTLV packet receiver 165 outputs the retained TLV packet to thetransmission slotter 164 in response to an instruction from thetransmission slotter 164.

The NTP packet generator 166 generates an NTP-type IP packet. The NTPpacket generator 166 arranges the IP packet in the form of TLV togenerate an NTP packet.

ARIB STD-44 edition 2.0 prescribes that an NTP packet contained in a TLVpacket be disposed at the head of the first slot for a frame among theslots allocated for each TLV stream ID. The aim of this is to suppressthe delay variation of NTP packets. Also, if two or more combinations ofthe modulation scheme and the coding rate are involved in the same TLVstream ID, an NTP packet may be disposed at the head of the first slotadopting the combination having the highest error resilience.

The NTP packet generator 166 receives a notification about the timing toinsert an NTP packet from the transmission slotter 164, and outputs theNTP packet containing that NTP time (system time) to the transmissionslotter 164. The NTP packet generator 166 may correct the NTP timethrough addition or subtraction of an externally-set offset.

The slot padding byte generator 167 generates a predetermined datasequence as slot padding bytes, in response to an instruction from thetransmission slotter 164. The first byte of the TLV packet is, as shownin FIG. 2, “0x7f”. As the slot padding bytes, the slot padding bytegenerator 167 generates a data sequence different from “0x7f”, e.g.,“0x7e”. The slot padding bytes are not limited to “0x7e”, but may be anyvalue other than “0x7f” where the first (or the most significant) twobits shall be ‘01’ in binary representation.

The slot padding byte generator 167 may generate the slot padding bytesso that the low 2 bits thereof will represent a remaining capacity ofthe last valid slot in the transmission main signals. That is, the slotpadding bytes may be “0x7e” when the remaining capacity is 3 bytes,“0x7d” when the remaining capacity is 2 bytes, and “0x7c” when theremaining capacity is 1 byte. The slot padding byte generator 167outputs the generated slot padding bytes to the transmission slotter164.

The TLV NULL packet generator 168 receives an instruction from thetransmission slotter 164 and generates a TLV NULL packet of theinstructed volume. The TLV NULL packet generator 168 outputs thegenerated TLV NULL packet to the transmission slotter 164. The TLV NULLpacket generator 168 may generate two or more TLV NULL packets. Forexample, if the instructed volume exceeds a predetermined volume, e.g.,1500 bytes, the TLV NULL packet generator 168 generates a plurality ofTLV NULL packets each up to 1500 bytes as a maximum volume. Note thatthe maximum volume of TLV NULL packet is not necessarily aligned withthat of regular TLV packet that contains an MMTP packet or an NTPpacket.

The transmission slotter 164 includes the selector 1641, a TLV bytenumber extractor 1642, a remainder calculator 1643, and a slotinformation multiplexer 1644.

The TLV byte number extractor 1642 receives the TLV packet from the TLVpacket receiver 165, or the NTP packet from the NTP packet generator166. The TLV byte number extractor 1642 extracts the data length, shownin FIG. 2, of the received TLV packet or the received NTP packet, andobtains the data volume included in the TLV packet or the NTP packet.The TLV byte number extractor 1642 outputs information about theobtained data volume to the remainder calculator 1643.

The remainder calculator 1643 receives the information about the framemain signal capacity from the capacity calculator 163, the informationabout the slot main signal capacity from the capacity calculator 163,and the information about the data volume from the TLV byte numberextractor 1642. The remainder calculator 1643 calculates a frameremaining capacity by subtracting the data volume from the frame mainsignal capacity one by one. The remainder calculator 1643 outputs thecalculated frame remaining capacity to the selector 1641. The remaindercalculator 1643 calculates a slot remaining capacity by subtracting thedata volume from the slot main signal capacity one by one. The remaindercalculator 1643 outputs the calculated slot remaining capacity to theselector 1641.

The selector 1641 stores the TLV packet, the NTP packet, or the TLV NULLpacket in the slot represented by the count value output from the slotnumber counter 161.

Upon storing the TLV packet, the NTP packet, or the TLV NULL packet inthe slot, the selector 1641 calculates the present slot remainingcapacity by subtracting the stored data volume from the slot remainingcapacity output from the remainder calculator 1643. Also, upon storingthe TLV packet, the NTP packet contained in a TLV packet, or the TLVNULL packet in the slot, the selector 1641 calculates the present frameremaining capacity by subtracting the stored data volume from the frameremaining capacity output from the remainder calculator 1643.

If storing the TLV packet, the NTP packet contained in a TLV packet, orthe TLV NULL packet in the slot has caused the slot remaining capacityof the last valid slot for the frame to be less than 4 bytes, theselector 1641 outputs an instruction to the slot padding byte generator167 to request slot padding bytes. In this instance, the selector 1641may request the slot padding byte generator 167 to provide the same slotpadding bytes, e.g., multiple bytes of “0x7e”.

If the slot remaining capacity is 3 bytes, the selector 1641 may request3 bytes of “0x7e”. If the slot remaining capacity is 2 bytes, theselector 1641 may request 2 bytes of “0x7d”. If the slot remainingcapacity is 1 byte, the selector 1641 may request 1 byte of “0x7c”. Therequest for the slot padding bytes by the selector 1641 is not limitedto this, and various forms may be assumed. For example, if the slotremaining capacity is 3 bytes, the selector 1641 may request for “0x7e”,“0x7d”, and “0x7c”. If the slot remaining capacity is 2 bytes, theselector 1641 may request for “0x7d” and “0x7c”. If the slot remainingcapacity is 1 byte, the selector 1641 may request for “0x7c”.

Based on the setting information from the setting information receiver162, the selector 1641 determines whether or not an NTP packet needs tobe stored at the head of the slot represented by the number of the countvalue output from the slot number counter 161. If yes, the selector 1641outputs an instruction to the NTP packet generator 166 to request for anNTP packet. The selector 1641 stores the NTP packet from the NTP packetgenerator 166 in the slot.

The selector 1641 instructs the TLV NULL packet generator 168 togenerate the TLV NULL packet having a volume that is appropriate for theframe remaining capacity and the slot remaining capacity. The selector1641, upon receiving the TLV NULL packet from the TLV NULL packetgenerator 168, stores the received TLV NULL packet in the slot.

The selector 1641 outputs the slot having stored the data to the slotinformation multiplexer 1644.

The slot information multiplexer 1644 receives the information about theframe main signal capacity from the capacity calculator 163, theinformation about the slot main signal capacity from the capacitycalculator 163, the setting information from the setting informationreceiver 162, and the slot from the selector 1641. The slot informationmultiplexer 1644 generates slot information about the received slotbased on the received frame main signal capacity, the received slot mainsignal capacity, and the received setting information. The slotinformation includes a synchronization signal, signal point arrangementinformation, and TMCC information. The signal point arrangementinformation indicates, for each slot, the head position of the firstpacket included and the tail position of the last packet included. TheTMCC information includes information about the transmission modecontaining the coding rate and the modulation scheme, information aboutthe TLV stream ID, and so on. The slot information multiplexer 1644multiplexes the generated slot information and the received slot, andoutputs the slot information-multiplexed slot to the transmissionprocessing apparatus 17. FIG. 5 is a schematic diagram illustrating theslot structures of the transmission main signals output from the slotinformation multiplexer 1644 to the transmission processing apparatus17.

The transmission processing apparatus 17 includes, for example, a CPU, amemory for use in the CPU's processing, and an FPGA, etc. to performgiven processing under the control of the CPU. With the CPU causing theFPGA to perform the given processing, the transmission processingapparatus 17 processes the transmission main signals. Specifically, thetransmission processing apparatus 17 receives the transmission mainsignals from the transmission slotting apparatus 16 and modulates thereceived transmission main signals by the modulation scheme assigned foreach slot. The transmission processing apparatus 17 performspredetermined transmission processing on the modulated signals andgenerates broadcast waves. The transmission processing apparatus 17transmits the broadcast waves.

The transmission processing apparatus 17 may include an LSI instead ofthe CPU and the FPGA. Also, the transmission processing apparatus 17 mayperform the given processing by software.

Next, the operation of the transmission slotting apparatus 16 configuredas above will be described in detail. FIG. 6 is a flowchart showing anexample of the processes to perform when the selector 1641 of FIG. 4stores received data in slots. Note that FIG. 6 explains an exemplarycase where one transmission mode is adopted for a frame, that is, wherethere is one combination of the modulation scheme and the coding rate inthe setting information.

First, the selector 1641 receives a count value from the slot numbercounter 161 (step S61). The selector 1641 determines whether or not thereceived count value is 1 (step S62). If the received count value is 1(Yes in step S62), the selector 1641 recognizes the start of a new frame(step S63). If the received count value is not 1 (No in step S62), theselector 1641 determines whether or not an NTP packet should be storedin the slot represented by the number of the count value (step S64).

If an NTP packet contained in a TLV packet needs to be stored in theslot (Yes in step S64), the selector 1641 stores the NTP packet at thehead of the current slot (step S65). If it is not necessary to store anNTP packet in the slot (No in step S64), the selector 1641 determineswhether or not the current slot is the last effective slot for thecurrent frame (step S66).

Upon storing the data in the current slot, the selector 1641 updates thepresent slot remaining capacity by subtracting the stored data volumefrom the slot remaining capacity output from the remainder calculator1643. Also, upon storing the data in the current slot, the selector 1641updates the present frame remaining capacity by subtracting the storeddata volume from the frame remaining capacity output from the remaindercalculator 1643 (step S67).

Next, the selector 1641 determines whether or not the slot remainingcapacity of the current slot is 0 (step S68). If the slot remainingcapacity of the current slot is 0 (Yes in step S68), the selector 1641determines whether or not the frame remaining capacity of the currentframe is 0 (step S69). If the slot remaining capacity of the currentslot is not 0 (No in step S68), the selector 1641 moves the processingto step S66.

If the frame remaining capacity of the current frame is 0 (Yes in stepS69), the selector 1641 stands by until the start of the next frame(step S610). If the frame remaining capacity of the current frame is not0 (No in step S69), the selector 1641 moves the processing to step S61.

In step S66, if the current slot is the last effective slot for thecurrent frame (Yes in step S66), the selector 1641 determines whether ornot the slot remaining capacity of the current slot is less than 4 bytes(step S611). If the current slot is not the last effective slot for thecurrent frame (No in step S66), the selector 1641 determines whether ornot there is a TLV packet to store in the current slot (step S612).

In step S611, if the slot remaining capacity of the current slot is lessthan 4 bytes (Yes in step S611), the selector 1641 stores slot paddingbytes output from the slot padding byte generator 167 in the region ofless than 4 bytes (step S613), and moves the processing to step S610.

In step S612, if there is a TLV packet to store in the current slot (Yesin step S612), the selector 1641 determines whether or not this TLVpacket can not be stored completely in the current slot, that is,whether or not storing the TLV packet in the current slot will make theframe remaining capacity of the current frame less than 0 (step S614).If there is no TLV packet to store in the current slot (No in stepS612), the selector 1641 stores the TLV NULL packet output from the TLVNULL packet generator 168 in the current slot (step S615), and moves theprocessing to step S67.

If storing the TLV packet in the current slot will make the frameremaining capacity of the current frame less than 0 (Yes in step S614),the selector 1641 couples together the current slot and the slots up tothe last valid slot for the current frame, and stores a TLV NULL packet,not this TLV packet, in the coupled slots (step S616). If storing theTLV packet in the current slot will not make the frame remainingcapacity of the current frame less than 0 (No in step S614), theselector 1641 determines whether or not storing the TLV packet in thecurrent slot will make the slot remaining capacity of the current slotless than 0 (step S617).

If storing the TLV packet in the current slot will make the slotremaining capacity of the current slot less than 0 (Yes in step S617),the selector 1641 divides the TLV packet into a first TLV packet of avolume that can be stored in the current slot, and a second TLV packetof the other portion (step S618). The selector 1641 stores the first TLVpacket after the division in the current slot (step S619), and moves theprocessing to step S67. If storing the TLV packet in the current slotwill make the slot remaining capacity of the current slot 0 or more (Noin step S617), the selector 1641 stores the TLV packet in the currentslot (step S620), and moves the processing to step S67.

By the selector 1641 performing the processes shown in FIG. 6, the slotgroup as shown in FIG. 7 will be output to the slot informationmultiplexer 1644. According to FIG. 7, the slot padding bytes are storedat the end of the last valid slot.

The case of one transmission mode for a frame has been described withFIG. 6. However, this is not a limitation. The selector 1641 canlikewise be operable in the cases where two or more transmission modesare adopted for a frame.

When there are two or more transmission modes for a frame, the capacitycalculator 163 calculates, as a frame main signal capacity, the capacityof the valid main signal portion for each transmission mode, based onthe setting information.

The remainder calculator 1643 calculates the frame remaining capacityfor each transmission mode by subtracting the data volume output fromthe TLV byte number extractor 1642 from the frame main signal capacitycalculated for each transmission mode.

The selector 1641 stores TLV packets in slots, following the assignmentof transmission modes to the slots as indicated by the settinginformation, and with reference to the frame remaining capacity and theslot remaining capacity.

FIG. 8 shows the slot structures for the case of one TLV stream and twotransmission modes. FIG. 8 assumes that the modulation scheme of thetransmission mode assigned to slots #1 to #60 has a larger multi-valuethan the modulation scheme of the transmission mode assigned to slots#61 to #120. In this instance, the transmission mode assigned to slots#61 to #120 is more resistant to interference, and therefore, an NTPpacket is disposed at the head of slot #61. Also, according to FIG. 8,slot padding bytes are stored at the end of the last valid slot in eachtransmission mode.

FIG. 9 shows the slot structures for the case of three TLV streams andthree transmission modes. In FIG. 9, the NTP packet for the transmissionmode assigned to slots #1 to #40 is stored at the head of slot #1, theNTP packet for the transmission mode assigned to slots #41 to #80 isstored at the head of slot #41, and the NTP packet for the transmissionmode assigned to slots #81 to #120 is stored at the head of slot #81.Also, according to FIG. 9, slot padding bytes are stored at the end ofthe last valid slot in the transmission mode assigned to slots #1 to#40.

As described above, the transmitting system 10 according to the firstembodiment calculates the frame main signal capacity and the slot mainsignal capacity by means of the capacity calculator 163 of thetransmission slotting apparatus 16. The remainder calculator 1643calculates the frame remaining capacity by subtracting the data volumeof a TLV packet from the frame main signal capacity, and calculates theslot remaining capacity by subtracting the data volume of the TLV packetfrom the slot main signal capacity. Furthermore, if the slot remainingcapacity of the last valid slot for a frame is less than 4 bytes, theselector 1641 stores slot padding bytes in the remaining region. Thisconfiguration enables the transmitting system 10 according to the firstembodiment to store data until the end of the last valid slot for aframe, even when the slot remaining capacity of the last valid slot forthe frame becomes less than 4 bytes due to the storage of TLV packets invalid slots.

Therefore, with the transmitting system 10 according to the firstembodiment, broadcast waves can be transmitted in a normal way even ifthe remaining capacity of the last valid slot for the frame has becomeless than 4 bytes due to the storage of TLV packets in valid slots forthe frame.

An option of coupling the 3-byte region left in the last valid slot fora preceding frame with the first slot for the succeeding frame so as tostore a TLV NULL packet in the coupled slots can also be considered.However, it is prescribed for the storage of an NTP packet that itsposition be at the head of the first slot. As such, this option fallsshort of the functions achieved by the transmitting system according tothe first embodiment.

Also, in the first embodiment, the slot padding byte generator 167generates multiple slot padding bytes according to remaining capacities.The selector 1641 stores the slot padding bytes according to theremaining capacities. This configuration allows the receiving system 20to comprehend, when it has received transmission main signals containingthe slot padding bytes, how many bytes the slot padding bytes accountfor.

[Receiving System 20]

FIG. 10 is a block diagram illustrating a configuration of the receivingsystem 20 shown in FIG. 1. The receiving system 20 of FIG. 10 includes areception processing apparatus 21, a transmission main signal receivingapparatus 22, a TLV separating apparatus 23, an IP separating apparatus24, an MMT separating apparatus 25, a decoder 26, and an additionalinformation interpreter 27.

The reception processing apparatus 21 receives broadcast waves sent viatransmission channels such as a broadcast network. The receptionprocessing apparatus 21 performs predetermined reception processing onthe broadcast waves and converts the received broadcast waves intotransmission main signals by the demodulation processing with ademodulation scheme corresponding to the modulation scheme assigned foreach slot. The reception processing apparatus 21 outputs thetransmission main signals to the transmission main signal receivingapparatus 22.

FIG. 11 is a block diagram illustrating an example of a functionalconfiguration of the transmission main signal receiving apparatus ofFIG. 10. FIG. 10 shows a data separator 221, an NTP time regenerator222, a slot information interpreter 223, and a slot padding byte remover224, and each of these functions is realized by a CPU causing an FPGA toperform given processing. The transmission main signal receivingapparatus 22 may include an LSI instead of the FPGA in order to realizethe functions shown in FIG. 11. The transmission main signal receivingapparatus 22 may also realize the functions shown in FIG. 11 bysoftware.

The data separator 221 receives the transmission main signals from thereception processing apparatus 21. The data separator 221 separates theslot information from the slots included in the received transmissionmain signals. The data separator 221 outputs the slot information afterthe separation to the slot information interpreter 223.

The data separator 221 refers to the slot headers of the slots includedin the received transmission main signals and takes out main signalsfrom the slots. The data separator 221 outputs the NTP packet includedin the main signals to the NTP time regenerator 222. Also, the dataseparator 221 outputs the data included in the main signals, other thanthe NTP packet, to the slot padding byte remover 224.

The NTP time regenerator 222 generates NTP time information based on theNTP packet output from the data separator 221. The NTP time regenerator222 adjusts an internally counting clock so that the generated NTP timeinformation and the internally counted time information synchronize witheach other, and outputs the internally counted time information to thesucceeding apparatus. The clock is adjusted by, for example, comparingthe NTP time information with the value of the internally counted timeinformation, and controlling the oscillation frequency of a VCXO(Voltage Controlled Crystal Oscillator) to clock up when the internallycounted time information is fast and to clock down when the internallycounted time information is slow.

The slot information interpreter 223 receives the slot information fromthe data separator 221. The slot information interpreter 223 interpretsthe signal point arrangement information and the TMCC informationincluded in the received slot information. The slot informationinterpreter 223 outputs the signal point arrangement information and theTMCC information to the slot padding byte remover 224.

The slot padding byte remover 224 memorizes in advance the datasequences to form slot padding bytes, for example, “0x7e”. The slotpadding byte remover 224 receives the signal point arrangementinformation and the TMCC information from the slot informationinterpreter 223. The slot padding byte remover 224 comprehends thetransmission mode of the transmission main signals, the tail position ofthe last packet in the last valid slot for a frame, and so on, based onthe received signal point arrangement information and the received TMCCinformation. The slot padding byte remover 224 determines, uponreceiving the data from the data separator 221, whether or not thememorized data sequence is present at this tail position. If thereceived data includes slot padding bytes, the slot padding byte remover224 removes at most 3 bytes of the slot padding bytes arranged from thetail position of the received data. The slot padding byte remover 224outputs the data after removal of the slot padding bytes, that is,outputs the TLV packets or TLV NULL packets to the TLV separatingapparatus.

The information memorized by the slot padding byte remover 224 is notlimited to data sequences. For example, the slot padding byte remover224 may memorize in advance that 3 bytes of data including “0x7e” areunnecessary if the slot includes “0x7e”, that 2 bytes of data including“0x7d” are unnecessary if the slot includes “0x7d”, and that 1 byte ofdata including “0x7c” is unnecessary if the slot includes “0x7c”. Inthis instance, the slot padding byte remover 224, according to the slotpadding bytes included in the data output from the data separator 221,removes the unnecessary data included in the received data.

The TLV separating apparatus 23 receives the TLV packet and the TLV NULLpacket from the transmission main signal receiving apparatus 22. The TLVseparating apparatus 23 takes out an IP packet from the received TLVpacket. The TLV separating apparatus 23 outputs the extracted IP packetto the IP separating apparatus 24.

The IP separating apparatus 24 receives the IP packet from the TLVseparating apparatus 23. The IP separating apparatus 24 takes out anMMTP packet from the received IP packet. The IP separating apparatus 24outputs the extracted MMTP packet to the MMT separating apparatus 25.

The MMT separating apparatus 25 receives the MMTP packet from the IPseparating apparatus 24. The MMT separating apparatus 25 takes outencoded signals and additional information from the received MMTPpacket. The MMT separating apparatus 25 outputs the extracted encodedsignals to the decoder 26, and outputs the extracted additionalinformation to the additional information interpreter 27.

The decoder 26 receives the encoded signals from the MMT separatingapparatus 25 and decodes them based on preset methods. The encodedsignals are thereby converted into video and/or audio signals. Thedecoder 26 outputs the video and/or audio signals to the succeedingapparatus.

The additional information interpreter 27 receives the additionalinformation from the MMT separating apparatus 25. The additionalinformation interpreter 27 outputs the information read from thereceived additional information to the succeeding apparatus.

As described above, the receiving system 20 according to the firstembodiment takes out main signals from slots by means of thetransmission main signal receiving apparatus 22. The transmission mainsignal receiving apparatus 22 memorizes in advance the data sequences toform slot padding bytes. Then, if the main signals include slot paddingbytes, the transmission main signal receiving apparatus 22 removes theslot padding bytes from the main signals. With this configuration, thetransmission main signal receiving apparatus 22 can take out TLV packetsfrom the transmission main signals in a normal way, even when the slotsthat form the transmission main signals include slot padding bytes.

Therefore, with the transmission main signal receiving apparatus 22according to the first embodiment, the receiving system 20 can achievenormal reception of broadcast waves even when the transmission mainsignals from the transmitting system 10 include slot padding bytes.

Second Embodiment

The first embodiment has been described using an example where thetransmission slotting apparatus 16 stores slot padding bytes in thevacant region if the slot remaining capacity of the last valid slot inthe transmission main signals becomes less than 4 bytes. For the secondembodiment, descriptions will be given using an example where atransmission slotting apparatus 18 stores packets in the slots so thatthe slot remaining capacity of the last valid slot in the transmissionmain signals will not become less than 4 bytes.

FIG. 12 is a block diagram illustrating an example of a functionalconfiguration of the transmission slotting apparatus 18 according to thesecond embodiment. FIG. 12 shows a slot number counter 161, a settinginformation receiver 162, a capacity calculator 163, a transmissionslotter 181, a TLV packet receiver 165, an NTP packet generator 166, anda TLV NULL packet generator 168, and each of these functions is realizedby a CPU causing an FPGA to perform given processing. The transmissionslotting apparatus 18 may include an LSI instead of the FPGA in order torealize the functions shown in FIG. 12. The transmission slottingapparatus 18 may also realize the functions shown in FIG. 12 bysoftware.

The transmission slotter 181 includes a selector 1811, a TLV byte numberextractor 1642, a remainder calculator 1643, and a slot informationmultiplexer 1644.

The selector 1811 stores a TLV packet, an NTP packet, or a TLV NULLpacket in the slot represented by the count value output from the slotnumber counter 161.

Upon storing the TLV packet, the NTP packet, or the TLV NULL packet inthe slot, the selector 1811 calculates the present slot remainingcapacity by subtracting the stored data volume from the slot remainingcapacity output from the remainder calculator 1643. Also, upon storingthe TLV packet, the NTP packet, or the TLV NULL packet in the slot, theselector 1811 calculates the present frame remaining capacity bysubtracting the stored data volume from the frame remaining capacityoutput from the remainder calculator 1643.

Based on the setting information from the setting information receiver162, the selector 1811 determines whether or not an NTP packet needs tobe stored at the head of the slot represented by the number of the countvalue output from the slot number counter 161. If yes, the selector 1811outputs an instruction to the NTP packet generator 166 to request an NTPpacket. The selector 1811 stores the NTP packet from the NTP packetgenerator 166 in the slot.

The selector 1811 instructs the TLV NULL packet generator 168 togenerate the TLV NULL packet having a volume that is appropriate for theframe remaining capacity and the slot remaining capacity. The selector1811, upon receiving the TLV NULL packet from the TLV NULL packetgenerator 168, stores the received TLV NULL packet in the slot.

The selector 1811 outputs the slot having stored the data to the slotinformation multiplexer 1644.

Next, the processes to perform when the selector 1811 of FIG. 12 storesreceived packets in slots will be described in detail. FIG. 13 is aflowchart showing the processes to perform when the selector 1811 storespackets in slots. FIG. 13 explains an exemplary case where onetransmission mode is adopted for a frame.

First, the selector 1811 receives a count value from the slot numbercounter 161 (step S131). The selector 1811 determines whether or not thereceived count value is 1 (step S132). If the received count value is 1(Yes in step S132), the selector 1811 recognizes the start of a newframe (step S133). If the received count value is not 1 (No in stepS132), the selector 1811 determines whether or not an NTP packet shouldbe stored in the slot represented by the number of the count value (stepS134).

If an NTP packet needs to be stored in the slot (Yes in step S134), theselector 1811 stores the NTP packet at the head of the current slot(step S135). If it is not necessary to store an NTP packet in the slot(No in step S134), the selector 1811 determines whether or not there isa TLV packet to store in the current slot (step S136).

Upon storing the data in the current slot, the selector 1811 updates thepresent slot remaining capacity by subtracting the stored data volumefrom the slot remaining capacity output from the remainder calculator1643. Also, upon storing the data in the current slot, the selector 1811updates the present frame remaining capacity by subtracting the storeddata volume from the frame remaining capacity output from the remaindercalculator 1643 (step S137).

Next, the selector 1811 determines whether or not the slot remainingcapacity of the current slot is 0 (step S138). If the slot remainingcapacity of the current slot is 0 (Yes in step S138), the selector 1811determines whether or not the frame remaining capacity of the currentframe is 0 (step S139). If the slot remaining capacity of the currentslot is not 0 (No in step S138), the selector 1811 moves the processingto step S136.

If the frame remaining capacity of the current frame is 0 (Yes in stepS139), the selector 1811 stands by until the start of the next frame(step S1310). If the frame remaining capacity of the current frame isnot 0 (No in step S139), the selector 1811 moves the processing to stepS131.

In step S136, if there is a TLV packet to store in the current slot (Yesin step S136), the selector 1811 determines whether or not storing theTLV packet in the current slot will make the frame remaining capacity ofthe current frame less than 4 bytes (step S1311). If there is no TLVpacket to store in the current slot (No in step S136), the selector 1811stores the TLV NULL packet output from the TLV NULL packet generator 168in the current slot (step S1312), and moves the processing to step S137.

If storing the TLV packet in the current slot will make the frameremaining capacity of the current frame less than 4 bytes (Yes in stepS1311), the selector 1811 couples together the current slot and theslots up to the last valid slot for the current frame, and stores a TLVNULL packet (or TLV NULL packets whose total size is equal to the frameremaining capacity) in the coupled slots (step S1313). If storing theTLV packet in the current slot will make the frame remaining capacity ofthe current frame 4 bytes or more (No in step S1311, the selector 1811determines whether or not storing the TLV packet in the current slotwill make the slot remaining capacity of the current slot less than 0(step S1314).

If storing the TLV packet in the current slot will make the slotremaining capacity of the current slot less than 0 (Yes in step S1314),the selector 1811 divides the TLV packet into a first TLV packet of avolume that can be stored in the current slot, and a second TLV packetof the other portion (step S1315). The selector 1811 stores the firstTLV packet after the division in the current slot (step S1316), andmoves the processing to step S137. If storing the TLV packet in thecurrent slot will make the slot remaining capacity of the current slot 0or more (No in step S1314), the selector 1811 stores the TLV packet inthe current slot (step S1317), and moves the processing to step S137.

The case of one transmission mode for a frame has been described withFIG. 13. However, this is not a limitation. The selector 1811 can belikewise operable in the cases where two or more transmission modes areadopted for a frame.

As described above, the transmitting system 10 according to the secondembodiment calculates the frame main signal capacity and the slot mainsignal capacity by means of the capacity calculator 163 of thetransmission slotting apparatus 18. The remainder calculator 1643calculates the frame remaining capacity by subtracting the data volumeof a TLV packet from the frame main signal capacity, and calculates theslot remaining capacity by subtracting the data volume of the TLV packetfrom the slot main signal capacity. Then, if storing the TLV packet inthe slot will make the frame remaining capacity of the current frameless than 4 bytes, the selector 1811 stores a TLV NULL packet up to theend of the slot without storing a TLV packet. This configuration enablesthe transmitting system 10 according to the second embodiment to storeTLV packets and TLV NULL packets until the end of the last valid slotfor a frame.

Therefore, with the transmitting system 10 according to the secondembodiment, it is possible to avoid the remaining capacity of the lastvalid slot for a frame becoming less than 4 bytes.

The first and second embodiments have been described using the exampleswhere the transmission slotting apparatus 16 or 18 stores TLV packets inthe main signal portions of slots. These TLV packets are, however,examples of variable-length packets that include information indicativeof a data type and information indicative of a data byte number. As thevariable-length packets that include information indicative of a datatype and information indicative of a data byte number, packets otherthan TLV packets, for example, Generic Stream Encapsulated (GSE) packetsmay be named. In this sense, the TLV multiplexing apparatus 15 may becalled a variable-length packet multiplexing apparatus.

Also, the first and second embodiments have been described so that a TLVpacket takes the minimum byte number of 4 bytes and that the selector1641 or 1811 operates according to whether or not the remaining capacityof the last valid slot is less than 4 bytes. However, the byte numberused by the selectors 1641 and 1811 as a criterion for theirdetermination is not limited to less than 4 bytes. Variable-lengthpackets can take a minimum byte number other than 4 bytes. If avariable-length packet takes a minimum byte number of, for example, 2bytes, the selector 1641 or 1811 may operate according to whether or notthe remaining capacity of the last valid slot is less than 2 bytes.

While certain embodiments have been described, they have been presentedby way of example only, and are not intended to limit the scope of theinvention. Indeed, the novel embodiments described herein may beembodied in a variety of other forms. Furthermore, various omissions,substitutions and changes in the form of the embodiments may be madewithout departing from the spirit of the invention. The accompanyingclaims and their equivalents are intended to cover such forms ormodifications as would fall within the scope and spirit.

The invention claimed is:
 1. A receiving apparatus comprising: at leastone processor or at least one circuit configured to: receive atransmission main signal comprising a plurality of slots, thetransmission main signal storing a data sequence of a predetermined databyte number at an end of a last valid slot for one frame among theslots, the data sequence being predetermined for each case of aremaining capacity of the last valid slot in the transmission mainsignal being less than a minimum byte number of a variable-length packetcomprising information indicative of a type of data and informationindicative of a byte number of the data; take out slot informationincluding information about the slots and a slot main signal from theslots of the received transmission main signal; interpret the slotinformation to acquire information about the slots, the acquiredinformation indicating a tail position of a last packet for each slotand a transmission mode containing a coding rate and a modulationscheme; comprehend a transmission mode of the transmission main signaland a tail position of a last packet in the last valid slot for oneframe based on the acquired information; determine a presence of thedata sequence in the tail position of the last packet in the last validslot based on a prestored data sequence; recognize a volume to remove,in accordance with the data sequence present; and remove the volume fromthe slot main signal.